Sigmund Freud, the man credited with founding psychoanalysis, stands as the towering figure in 20th century psychological theory.

Born in Moravia and trained in Vienna, Freud published a number of important works including "The Interpretation of Dreams" (1900). It was Freud's belief that much of human thinking occurs in the part of the mind he termed the "subconscious."

He held that the unconscious sexual drives of infancy and early childhood help shape personality. Forced to flee Nazi Austria in 1938, Freud made his way to London, where he died shortly after the outbreak of World War II.